exercise thresholds Flashcards
what are the 2 ways to measure lactate threshold
measure blood lactate
measuring ventilatory and gas exchange thresholds
what occurs with the onset of exercise in the moderate domain (before GET)
linear increases in O2 consumption, CO2 production, and VE
steady metabolic state
blood lactate nad H+ are consistent (lactate near 0)
values remain stable as long as you stay in domain
what is the energy source in the moderate domain (below GET)
all energy from aerobic glycolysis
- not much lactate and H+ produced
after a few mins, fat oxidation is the predominant energy system
how can moderate intensity be determined
VO2 reaches steady state within 2-3 min
blood lactate remains around resting values
why is there a lack of increase in blood lactate during moderate intensity exercise
due to demand for ATP that can be met by aerobic glycolysis and glycogenolysis
- rate of pyruvate porduction is approx equal to the uptake/oxidation of pyruvate (low conversion to lactate)
what occurs with the onset of exercise in the heavy domain (between GET and RCP)
linear increases in O2 consumption
not linear increases in CO2 production
VE increases at a faster rate in relation to increased workload/VO2
steady metabolic state
blood lactate and H+ increase and then reach steady state (production and clearance still at equilbrium)
what is MLSS
maximal lactate steady state
- highest level of lactate production that can continue without further increase (steady state)
- occurs at RCP
- highest point at which steady state responses in VO2 and lactate are possible
what occurs at the GET compared to moderate domain
CO2 and H+ are buffered by bicarbonate = increase in CO2 production
- increased CO2 content in expired air due to increased CO2 removal (buffering)
activation of glycolytic pathway increases the rate of H+ production
- lactate produced but rate of clearance is equal
what is the extrinsic regulation of cardioresp function in the heavy domain
producing more H+ but able to buffer
increased metabolites activate resp system
resp system increases HR and muscle contraction
faster CR responses during exercise
how can heavy intensity be determined
steady state VO2 reached in 10-15 min
greater blood lactate levels
steady metabolic state still reached through buffering
why does blood lactate increase in the heavy domain
greater metabolic demand
increase in pyruvate production
lactate production exceeds the rate of uptake and oxidation
what occurs with the onset of exercise in the severe domain (after RCP)
linear O2 consumption
nonlinear CO2 production
non linear increase in VE
hyperventilation can’t compensate for the rise in H+
- VE increases out of proportion to VCO2
no metabolic steady state
blood lactate/H+ production exceeds the clearance rate
why does ventilation go down in the moderate domain
neural system activated first therefore high ventilation
then it adjusts and goes down based on humoral factors
(with enough time it will be flat)
what is the extrinsic regulation of cardioresp function in the severe domain
pH drops
increase in hyperventilation
body can’t keep up and buffer more and more metabolites
CR capacity is unable to buffer
why is there a greater increase in lactate in the severe domain
responds to high ATP demand with a faster rate of glycolysis
- exceeds the ability of mito to accept increased production of pyruvate AND the capacity of the system to buffer the increased H+ (from lactate-pyruvate conversion)
